The present invention relates to a surface position detection device and an exposure apparatus and an exposure method achieved by utilizing the detection device. More specifically, it relates to detection of the surface position of a photosensitive substrate in a projection exposure apparatus which is employed to transfer a mask pattern onto the photosensitive substrate in the lithography process implemented to manufacture a micro device such as a semiconductor element, a liquid crystal display element, an image-capturing element (such as a CCD) and a thin film magnetic head.
Surface position detection devices ideal in application in projection exposure apparatuses in the known art include the oblique incidence-type surface position detection device disclosed by the applicant of the present invention in Japanese Unexamined Patent Publication No. 42205/1981. In this surface position detection device, detection light is irradiated from a diagonal direction onto a semiconductor wafer set at a position which allows a mask pattern to be transferred onto it through a projection lens. More specifically, a slit pattern is projected onto the detection target surface, i.e., the surface of the semiconductor wafer, by ensuring that the direction along which the long side of the slit pattern extends is perpendicular to the entrance plane (the plane formed of the incident light and the reflected light). Then, by condensing the reflected light, a pattern image is reformed on a detection surface of a means for detection constituted of a photoelectric conversion element and the position at which the pattern image is formed on the detection surface is detected.
In the surface position detection device structured as described above, when the surface of the semiconductor wafer constituting the detection target surface becomes displaced along the vertical direction (displaced along the optical axis of the projection lens), the slit reflection light entering the means for detection becomes shifted laterally along the widthwise direction (the direction along which the short side extends) in correspondence to the vertical displacement. The position of the surface of the semiconductor wafer along the vertical direction is detected based upon the degree of the lateral shift. Thus, based upon the results of the detection, a decision is made as to whether or not the wafer surface is aligned at the focus reference position of the projection lens, i.e., whether or not the wafer surface is aligned on a plane that is conjugate with the surface of the mask pattern projected by the projection lens.
In addition, Japanese Unexamined Patent Publication No. 97045/1994 filed by the applicant of the present invention discloses an improvement on the oblique incidence-type surface position detection device described above, which is capable of performing position detection over a wide area of the detection target surface. This surface position detection device is provided with a projection optical system that projects an image of a specific pattern formed at a first surface onto a wafer surface constituting a detection target surface and a condenser optical system that condenses a light beam having been reflected at the detection target surface and forms an image of the specific pattern on a second surface at, which a light-receiving slit is formed. In addition, Scheimpflug condition is achieved for the first surface and the detection target surface with respect to the projection optical system and Scheimpflug condition is achieved for the detection target surface and the second surface with respect to the condenser optical system.
In this surface position detection device, the projection optical system and the condenser optical system each achieve bilateral telecentricity, to assure that uniform magnification is achieved at the various points on the first surface and the various corresponding points on the detection target surface over the entire surface areas and that uniform magnification is achieved at various points on the detection target surface and various corresponding points on the second surface over, the entire surface areas. By assuming these structural features, a uniform degree of detection accuracy is achieved over the entire detection area on the detection target surface through a detection method based upon the principle of photoelectric microscopy in which the image of the specific pattern formed on the second surface and the light receiving slit are scanned relative to each other to synchronously detect light modulation signals.